1. Field of the Invention
The present invention relates to a system for transmitting electric power into a bore hole.
2. Description of the Related Art
Such a system is known and described in paper SPE/IADC 52791 of the Society of Petroleum Engineers, entitled “Electric coiled tubing drilling: a smarter CT drilling system” by D. R. Turner et. al. In the known system, an electrically powered bottom hole assembly is connected to an electric coiled tubing that reaches into a bore hole. The electric coiled tubing holds an electric transmission line, for powering a down hole electric DC motor. The peak power output of this motor is 28 HP, corresponding to some 21 kW.
This system is not considered suitable of transmitting much higher electric power at the motor voltage, for instance as high as 100 to 400 kW, since that would require very large cross section cable which would not fit in the coiled tubing. Moreover, such a cable would become so heavy that it would not be able to pull its own weight if it reaches into a typical bore hole suitable for production of hydrocarbons.